electrical engineering Mcqs
1. economics of power generation2. analog electronics3. solid state switching circuits4. parallel circuits5. switchgear and protection6. op amp circuits7. transistor audio power amplifiers8. electrostatics9. heating and welding10. multi stage transistor amplifiers11. passive filters12. network theorems13. regulated d c power supply14. a c fundamentals circuits and circuit theory15. electromagnetic induction16. power electronics17. magnetism and electromagnetism18. transformers19. modulation and demodulation20. d c generators21. semiconductor theory22. single phase induction motors23. semiconductor diode24. hybrid parameters25. digital electronics26. oscillators27. earthing or grounding28. single stage transistor amplifiers29. d c motors30. transistor biasing31. amplifiers with negative feedback32. basic electrical33. electronic instruments34. synchronous motors35. field effect transistors fet36. magnetic circuit37. control systems38. industrial drives39. power generation40. series parallel circuits41. transistor tuned amplifiers42. electrical engineering materials43. rectifiers and converters44. integrated circuits45. scr silicon controlled rectifiers46. cables47. polyphase induction motors48. measurement and instrumentation49. transistors50. electrical machine design51. electrolysis and storage of batteries52. electric traction53. transmission and distribution
801. Which of the following statement about D.C. generators is false ?
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A. Compensating winding in a D.C. machine helps in commutation

B. In a D. C. generator interpoles winding is connected in series with the armature winding

C. Back pitch and front pitch are both odd and approximately equal to the pole pitch

D. Equilizing bus bars are used with parallel running of D.C. shunt generators
802. Which D.C. motor will be suitable along with flywheel for intermittent light and heavy loads?
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A. Cumulatively compounded motor

B. Differentially compounded motor

C. Shunt motor

D. Series motor

803. In D.C. machines fractional pitch winding is used__________?
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A. to increase the generated e.m.f.

B. to reduce copper losses

C. to reduce the sparking

D. to improve cooling

804. A D.C. series motor is that which______________?
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A. has a poor torque

B. has its field winding consisting of thick wire and less turns

C. has almost constant speed

D. can be started easily without load

805. The demagnetising component of armature reaction in a D.C. generator___________?
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A. increases armature speed

B. reduces generator e.m.f.

C. results in sparking trouble

D. reduces interpoles flux density

806. Which of the following method is used for the speed control of DC shunt motor?
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A. voltage control method

B. all of the above

C. rheostat control method

D. flux control method

807. In a D.C. generator in case the resistance of the field winding is increased, then output voltage will____________?
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A. increase

B. remain unaffected

C. decrease

D. fluctuate heavily

808. The speed of a D.C. series motor is_____________?
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A. proportional to the armature current

B. proportional to the square of the armature current

C. proportional to field current

D. inversely proportional to the armature current
809. In a D.C. machine stray loss is the sum of_____________?
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A. shunt field copper loss and mechanical loss

B. total copper loss and mechanical loss

C. armature copper loss and iron loss

D. iron loss and mechanical loss
810. Welding generator will have____________?
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A. duplex wave winding

B. delta winding

C. lap winding

D. wave winding

811. The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by______________?
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A. increasing the excitation current

B. none of the above methods

C. decreasing the armature current

D. reducing the field current

E. increasing the armature current

812. Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ?
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A. Equilizer rings

B. Eye bolt

C. Dummy coils

D. Commutator
813. A dc series motor should not be started on no load because it would___________?
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A. not develop starting torque

B. fail to start without load

C. run at dangerously high speed

D. draw more current without producing sufficient torque

814. D.C. generators are connected to the busbars or disconnected from them only under the floating condition________________?
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A. to avoid sudden loading of the primemover

B. to avoid mechanicaljerk to the shaft

C. all above

D. to avoid burning of switch contacts

815. Which of the following could be lamina-proximately the thickness of laminations of a D.C. machine ?
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A. 0.005 mm

B. 5 m

C. 0.5 m

D. 0.05 mm

816. Why are the D.C. motors preferred for traction applications ?
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A. Torque and speed are inversely proportional to armature current

B. Torque is proportional to armature current

C. The speed is inversely proportional to the torque and the torque is proportional to square of armature current

D. Torque is proportional to square root of armature current

817. In a DC motor the inter-pole winding is connected in________________?
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A. parallel with armature winding

B. series speed armature winding

C. parallel big field winding

D. series with field winding

818. If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to______________?
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A. increase the speed of primemover

B. reverse the field connections

C. check armature insulation resistance

D. increase the field resistance

819. In over compounded generator, full load terminal voltage is______________?
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A. equal to no-load terminal voltage

B. more than no load terminal voltage

C. less than no load terminal voltage

D. almost zero

820. The armature of D.C. generator is laminated to_______________?
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A. insulate the core

B. reduce the bulk

C. reduce eddy current loss

D. provide the bulk

821. Which of the following load normally needs starting torque more than the rated torque?
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A. Centrifugal pumps

B. Air compressors

C. Conveyors

D. Blowers

822. The hysteresis loss in a D.C. machine least depends on____________?
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A. Frequency of magnetic reversals

B. Rate of flow of ventilating air

C. Maximum value of flux density

D. Volume and grade of iron

823. The terminal voltage of a D.C. shunt generator drops on load because of all of the following reasons except:_____________?
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A. field weakening due to armature reaction and armature

B. armature resistance drop

C. armature reaction

D. commutation
824. In D.C. shunt motors as load is reduced__________________?
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A. the speed will increase abruptly

B. the speed will remain almost/constant

C. the speed will reduce

D. the speed will increase in proportion to reduction in load

825. The rapid wear of brushes takes place due to____________?
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A. rough commutator bars

B. all of the above factors

C. excessive spring pressure

D. high mica insulation between com-mutation bars

E. abrasion from dust

826. In D.C. machines the residual magnetism is of the order of_________________?
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A. 20 to 25 per cent

B. 50 to 75 per cent

C. 10 to 15 per cent

D. 2 to 3 per cent
827. In Ward-Leonard control the lower limit of speed is imposed by________?
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A. core losses of motor

B. all of the above

C. residual magnetism of the generator

D. mechanical losses of motor and generator together

828. Which of the following motors is usually used in house-hold refrigerators ?
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A. D.C. series motor

B. Synchronous motor

C. D.C. shunt motor

D. Reluctance motor

E. Single phase induction motor (split phase start or induction run motor)
829. Open circuited armature coil of a D.C. machine is________________?
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A. identified by the scarring of the commutator segment to which open circuited coil is connected

B. indicated by a spark completely around the commutator

C. both A. and (b)

D. none of the above

830. In D.C. generators on no-load, the air gap flux distribution in space is______________?
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A. pulsating

B. triangular

C. sinusoidal

D. flat topped
831. The resistance of armature winding depends on
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A. all of the above

B. length of conductor

C. number of conductors

D. cross-sectional area of the conductor

832. Sparking at the commutator of a D.C. motor may result in____________?
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A. damage to commutator segments

B. damage to commutator insulation

C. increased power consumption

D. all of the above
833. The frame of an induction motor is usually made of____________?
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A. cast iron

B. bronze

C. silicon steel

D. aluminium

834. D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the________________?
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A. shunt motor

B. compound motor

C. series motor

D. any of the above

835. If the field of a D.C. shunt motor gets opened while motor is running______________?
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A. the motor will attain dangerously high speed 1

B. the speed of motor will be reduced %

C. the motor will continue to nuvat constant speed

D. the armature current will reduce

836. Armature reaction in a generator results in_____________?
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A. damagnetising the center of all poles

B. demagnetisation of trailing pole tip and magnetisation of leading pole tip

C. magnetising the center of all poles

D. demagnetisation of leading pole tip and magnetisation of trailing pole tip
837. In case-the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be______________?
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A. 100%

B. less than 50%

C. anywhere between 75% and 90%

D. around 90%

838. The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is______________?
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A. 6

B. 8

C. 2

D. 4
839. In a four-pole D.C. machine____________?
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A. all the four poles are south poles

B. alternate poles are north and south

C. two north poles follow two south poles

D. all the four poles are north poles

840. A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be_____________?
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A. 220 V

B. about 50 V

C. about 2 V

D. zero

841. In case of a flat compounded generator:
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A. generated voltage is proportional to the load on the generator

B. voltage remains constant irrespective of the load

C. voltage generated is less than the rated voltage

D. speed varies in proportion to the load on the generator

842. The insulating material used between the commutator segments is normally_____________?
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A. mica

B. paper

C. insulating varnish

D. graphite

843. The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be_____________?
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A. 620 V

B. 580 V

C. 640 V

D. 600 V

844. In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to
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A. 25% of the previous value

B. 50% of the previous value

C. none of the above

D. 100% of the previous value

E. 10% of the previous value

845. If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be________________?
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A. demagnetisation only

B. cross magnetisation only

C. crossmagnetisation as well as demagnetising

D. cross magnetisation as well as magnetisation

846. Following D.C. generator will be in a position to build up without any residual magnetism in the poles______________?
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A. shunt generator

B. self-excited generator

C. series generator

D. compound generator

847. In a manual shunt motor starter?
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A. over load relay is connected in series and no volt relay in parallel with the load

B. over load relay is connected in parallel and no volt relay in series with the load

C. over load relay and no volt relay are both connected in series with the load

D. over load relay and no volt relay are both connected in parallel with the load

848. For which types of D.C. motor, dynamic braking is generally used ?
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A. Shunt motors

B. Series motors

C. All of the above

D. Compound motors

849. When two D.C. generators are running in parallel an equilizer bar is used______________?
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A. to increase the series flux

B. to increase the generated e.m.f.

C. to reduce the combined effect of ar-mature reaction of both the machines

D. so that the two identical machines will pass approximately equal currents to the load
850. If the field winding resistance of a DC shunt motor is increases, its speed will____________?
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A. increases

B. the field winding resistance of a DC shunt motor is increases, its speed will

C. none of the above

D. remains same

E. decreases